BSD 4_3_Reno release

[unix-history] / usr / src / lib / libmp / mdiv.c

#ifndef lint
static char sccsid[] = "@(#)mdiv.c      5.2 (Berkeley) 3/2/87";
#endif not lint

#include <mp.h>
mdiv(a,b,q,r) MINT *a,*b,*q,*r;
{       MINT x,y;
       int sign;
       sign=1;
       x.val=a->val;
       y.val=b->val;
       x.len=a->len;
       if(x.len<0) {sign= -1; x.len= -x.len;}
       y.len=b->len;
       if(y.len<0) {sign= -sign; y.len= -y.len;}
       xfree(q);
       xfree(r);
       m_div(&x,&y,q,r);
       if(sign==-1)
       {       q->len= -q->len;
               r->len = - r->len;
       }
       return;
}
m_dsb(q,n,a,b) short *a,*b;
{       long int x,qx;
       int borrow,j;
       short u;
       qx=q;
       borrow=0;
       for(j=0;j<n;j++)
       {       x=borrow-a[j]*qx+b[j];
               b[j]=x&077777;
               borrow=x>>15;
       }
       x=borrow+b[j];
       b[j]=x&077777;
       if(x>>15 ==0) { return(0);}
       borrow=0;
       for(j=0;j<n;j++)
       {       u=a[j]+b[j]+borrow;
               if(u<0) borrow=1;
               else borrow=0;
               b[j]=u&077777;
       }
       { return(1);}
}
m_trq(v1,v2,u1,u2,u3)
{       long int d;
       long int x1;
       if(u1==v1) d=077777;
       else d=(u1*0100000L+u2)/v1;
       while(1)
       {       x1=u1*0100000L+u2-v1*d;
               x1=x1*0100000L+u3-v2*d;
               if(x1<0) d=d-1;
               else {return(d);}
       }
}
m_div(a,b,q,r) MINT *a,*b,*q,*r;
{       MINT u,v,x,w;
       short d,*qval;
       int qq,n,v1,v2,j;
       u.len=v.len=x.len=w.len=0;
       if(b->len==0) { fatal("mdiv divide by zero"); return;}
       if(b->len==1)
       {       r->val=xalloc(1,"m_div1");
               sdiv(a,b->val[0],q,r->val);
               if(r->val[0]==0)
               {       shfree(r->val);
                       r->len=0;
               }
               else r->len=1;
               return;
       }
       if(a->len < b->len)
       {       q->len=0;
               r->len=a->len;
               r->val=xalloc(r->len,"m_div2");
               for(qq=0;qq<r->len;qq++) r->val[qq]=a->val[qq];
               return;
       }
       x.len=1;
       x.val = &d;
       n=b->len;
       d=0100000L/(b->val[n-1]+1L);
       mult(a,&x,&u); /*subtle: relies on fact that mult allocates extra space */
       mult(b,&x,&v);
       v1=v.val[n-1];
       v2=v.val[n-2];
       qval=xalloc(a->len-n+1,"m_div3");
       for(j=a->len-n;j>=0;j--)
       {       qq=m_trq(v1,v2,u.val[j+n],u.val[j+n-1],u.val[j+n-2]);
               if(m_dsb(qq,n,v.val,&(u.val[j]))) qq -= 1;
               qval[j]=qq;
       }
       x.len=n;
       x.val=u.val;
       mcan(&x);
       sdiv(&x,d,&w,(short *)&qq);
       r->len=w.len;
       r->val=w.val;
       q->val=qval;
       qq=a->len-n+1;
       if(qq>0 && qval[qq-1]==0) qq -= 1;
       q->len=qq;
       if(qq==0) shfree(qval);
       if(x.len!=0) xfree(&u);
       xfree(&v);
       return;
}